There is a growing need for a flat-panel display as an image display device with the wide spreading use of information terminals. In addition, there are increasing opportunities, in which information, which has been conventionally provided by paper medium, is digitized with further advancement of informatization. Particularly, the needs for an electronic paper or a digital paper as a thin and light weight mobile display media, which can be easily held and carried, are recently increased (see Patent document 1).
Generally, in a flat panel display device, its display medium is formed by using an element such as a liquid crystal, an organic EL (organic electroluminescence), and an electrophoresis. In such display media, a technology which uses an active drive element (TFT element) as an image drive element has become a mainstream in order to secure the homogeneity of screen luminosity and screen rewriting speed and so forth. In the conventional display device, such TFT elements are formed on a glass substrate, thereafter a liquid crystal element or an organic EL element and so forth is sealed.
As a TFT element, semiconductors including a-Si (amorphous silicon) and p-Si (polysilicon) can be mainly used. These Si semiconductors (together with metal films, as necessary) are multilayered, and each of a source electrode, a drain electrode and a gate electrode is sequentially stacked on a substrate, thereby a TFT element is manufactured.
In the conventional process of manufacturing a TFT element using Si materials includes one or more steps using a high temperature, so that an additional restriction that the material of the substrate should resists a high process temperature comes to be added. For this reason, there is no way to select a glass as the material of the substrate in practice. In the meanwhile, it is possible to use a quartz substrate. However a quartz substrate is so expensive that an economical problem arises in scaling up of the display panels using a quartz substrate. Therefore, a glass substrate is generally used as a substrate for forming such TFT elements.
However, when the thin display panel described above is constituted using the conventionally known glass substrate, there is a possibility that such a display panel has a heavy weight, lacks a flexibility and breaks due to a shock when it would be fallen down. These problems, which arose from the formation of a TFT element on a glass substrate, are not desirable to meet the needs for a portable thin display having light weight with the advancement of informatization.
From the standpoint of a substrate having flexibility and light weight so as to meet the needs for a portable thin display having light weight, development of a flexible semiconductor device wherein TFT elements are formed on a resin substrate (plastic substrate) has been carried out. For example, Patent document 2 discloses a technique in which a TFT element is formed on a substrate (for example, glass substrate) by a process which is almost the same as conventional process, and then the TFT element is peeled from the glass substrate and transferred onto a resin substrate. In this technique, a TFT element is formed on a glass substrate and is adhered to a resin substrate via a sealing layer using such as an acrylic resin, and then the glass substrate is peeled off and the TFT element is transferred onto the resin substrate, thereby a semiconductor device is obtained.